Today, one of the directions in the industry of materials for cosmetology and plastic surgery are the development and production of mesotherapeutic threads (microthreads, 3D threads), the cosmetological threads used to perform the minimally invasive technique of threadlifting. The method consists in the subcutaneous injection of mesothreads in order to reinforce facial tissues and eliminate ptosis by means of biodegradable mesothreads that allow for modelling tissues in any areas including face and body parts that are not treatable using other technologies. A mesothread is a thread used to perform 3D modelling of face and body contours and to connect tissues to form a scar, or epithelization. Mesothreads can even out the skin relief thanks to the compressing activity of threads introduced subcutaneously. An essential condition for the bioreinforcement to have clinical effect is the creation of stringers that ensure pronounced and long-lasting lifting of the soft tissues.
Mesothreads are made using threads with a monofilament structure, high biocompatibility, optimum physical and mechanical properties (durability, stiffness, strain characteristics, thread's “memory effect”) and resistance to infection. After having performed their functions and formed a normal durable scar, the mesothreads should completely degrade, their degradation products being included into the body's metabolism without negatively affecting it. In other words, the thread lifting procedure should be reversible (maintaining the effect for a period between 0.5 and 2 years) and compatible with other anti-age procedures.
At present, there are various mesothreads made from different materials. Aesthetic therapy uses skin lifting using golden threads (e.g., patent KR 1020140071885, Dec. 6, 2014). This method is efficient but still has its drawbacks. The golden threads do not biodegrade and can cause allergies because they contain metals; patients who have had their skin lifted using golden threads are not allowed to undergo most instrumental physiotherapeutic procedures and plastic surgeries anymore.
The most suitable material for making mesothreads are biodegradable polymers. One of the most widely used among them is now polydioxanone (PDO). Threads made from it have outstanding biocompatibility and degrade within 8 month, are elastic, do not produce a “saw” effect and are atraumatic.
At the technical level, the RF patent No. 2524610, published in 2014 (prototype), describing a multi-component mesothread consisting of a polydioxanone core and a coat made from polyglycolic acid, used to correct aesthetic and age-related skin changes.
Following are the drawbacks of PDO-based mesothreads: such threads fully degrade in the human organism by means of hydrolysis within 4-8 months; the intermediate hydrolysis products accumulate in the organism next to the areas where the mesothreads are injected. Since the hydrolysis products of PDO-based mesothreads have acidic nature, they cause a local decrease in the pH level of the environment and, therefore, a moderate (low to average) tissue reaction. So far, there is no way to avoid it, since PDO degrades through water hydrolysis only, where acidic environment triggers the autocatalytic effect that accelerates further degradation of PDO. Studies show that PDO suppresses the adhesion of macrophages to some extent and causes the effect of local immunosuppression in the implantation area: there is a decrease in both the levels of humoral and cell immunity, mostly NK lymphocytes. The decreased amount of NK lymphocytes results in the development of oncological diseases and aggravations in the course of viral infections.